There are several types of building lighting systems in widespread use. Incandescent lighting systems are widely used currently. In an incandescent light AC current is passed through a filament housed in a vacuum bulb. The filament glows and gives off light.
Incandescent light bulbs also have a drawback as they burn hot, and are inefficient in their use of power when compared to florescent lights. Because of the inherent inefficiency, incandescent light bulbs are falling into disfavor.
Another popular lighting system employs a florescent light system. Florescent light systems employ a gas-filled sealed tube. By passing current through the gas, the gas is caused to glow, to thereby give of light. Florescent lights, while highly popular, also have drawbacks. Florescent lights raise health and/or environmental concerns, since florescent lights typically include mercury that is highly poisonous and creates an environmental hazard.
Another difficulty is that the light given off by most florescent lights is a very “cool” (blush) light that, while doing a fine job to illuminate a space, does not contain the warmer tones of an incandescent light bulb. Further, unlike incandescent lights, florescent lights are not well adapted to provide a variable light output, such as can be accomplished through a dimmer without additional circuitry that has a significant impact on the cost of the bulb.
It is noteworthy that AC current is normally used to drive both incandescent and florescent lights that are found in homes and commercial buildings. Because of the popularity of these lights, most buildings are designed to have 120 volt AC current delivered to the building or structure by an electric utility. The delivered current is then distributed within the structure as 120 volt AC current and in some cases, 240 volt AC current), in the United States. Within the building, the 120 volt AC current is delivered directly to rooms through wires, that are coupled to an incandescent or florescent light bulb, to thereby power the bulb. This arrangement works well since incandescent and florescent bulbs are best driven by such AC current, at least in the United States.
In addition to the incandescent and florescent bulb discussed above, other light bulbs exist that are used in certain applications, such as mercury vapor light bulbs, metal halide and other bulbs. These bulbs are also driven by alternating current.
Another, increasingly popular type of light bulb is an “LED bulb”, since the light source primarily comprises a light emitting diode or LED. LED light bulbs are gaining favor because they are capable of providing a large amount of light and typically have a rather long life span. However, probably the most desirable feature of LED lights is that they provide a large amount of light with a very low amount of power consumption, and thus, are highly efficient, and inexpensive to operate since they require much less power than either an incandescent or florescent bulb. Some estimates suggest that even with the higher initial purchase cost, purchasing and operating an LED light will cost significantly less than an incandescent bulb, and about the same as a florescent bulb.
Currently, LED bulbs exist that are capable of being used in conventional housing systems and building systems. For example, LED bulbs exist that have a threaded base that can be threadedly engaged into a threaded light bulb socket of the type that currently houses an incandescent bulb.
There exists a significant difference in the way that LED light bulbs operate, when compared with most incandescent or florescent bulbs, as LED bulbs tend to be driven by DC current, rather than AC current. In order to accommodate this, currently existing LED bulbs often contain not only a bulb component (which may comprise from one to a large plurality of individual LED bulbs), but also a driver component. The driver is provided for converting alternating current into direct current so that the bulb can be powered by direct current.
One difficulty with the use of such driver-containing LED bulbs is that they can be expensive to replace. Since current “plug in an AC light socket” type LED bulbs include both a bulb and its chip-based driver, the price of the bulb reflects not only the cost of the bulb but also of the driver. It has been found by the Applicant that the bulb and the driver will often have different useful lives. However, since the bulb and the driver are combined in one inseparable unit, the useful life of the component with the shortest useful life typically governs the lifetime of the combined device, since, for example, when the driver burns out, the driver and bulb must be replaced as a unit. An additional issue relates to flexibility of the unit, since the driver and the bulb are combined.
Therefore, one object of the present invention is to provide a lighting device that improves upon current known devices.